Which statement best describes a transcriptional coactivator?

Which statement best describes a transcriptional coactivator?

• A. A protein that binds DNA to repress transcription.
• B. A protein that degrades transcription factors.
• C. A protein that interacts with transcription factors to increase transcription without binding DNA directly.
• D. A protein that modifies tRNA during translation.

Answer: (C)

Transcriptional coactivators boost gene expression by working through protein–protein interactions with transcription factors and the transcription machinery, not by binding the DNA themselves. They often act as bridges or scaffolds, recruiting the Mediator complex and chromatin-modifying enzymes to the promoter region. This helps RNA polymerase II access the DNA and begin transcription more efficiently. Because they lack DNA-binding domains, coactivators don’t bind promoter DNA directly; their role is to enhance transcription through interactions with other proteins. This fits the idea that a transcriptional coactivator interacts with transcription factors to increase transcription without directly binding DNA. In contrast, a protein that binds DNA to repress transcription would be a repressor, not a coactivator. A protein that degrades transcription factors would reduce transcription by lowering factor availability. And a protein that modifies tRNA operates during translation, not transcription.

Transcriptional coactivators boost gene expression by working through protein–protein interactions with transcription factors and the transcription machinery, not by binding the DNA themselves. They often act as bridges or scaffolds, recruiting the Mediator complex and chromatin-modifying enzymes to the promoter region. This helps RNA polymerase II access the DNA and begin transcription more efficiently. Because they lack DNA-binding domains, coactivators don’t bind promoter DNA directly; their role is to enhance transcription through interactions with other proteins.

This fits the idea that a transcriptional coactivator interacts with transcription factors to increase transcription without directly binding DNA. In contrast, a protein that binds DNA to repress transcription would be a repressor, not a coactivator. A protein that degrades transcription factors would reduce transcription by lowering factor availability. And a protein that modifies tRNA operates during translation, not transcription.